In a manufacturing line of a semiconductor substrate, a thin film substrate, or the like, in order to monitor a dust generation situation of a manufacturing apparatus, a defect on the surface of the semiconductor substrate, thin film substrate, or the like is inspected.
Hitherto, as a technique for detecting a micro defect on the surface of an inspection object such as a semiconductor substrate or the like, for example, as disclosed in the specification of U.S. Pat. No. 5,798,829, there is such a technique that a collected laser light flux is fixedly irradiated onto the surface of the semiconductor substrate (an illuminated area which is formed onto the surface of the semiconductor substrate by the laser light flux at this time is called an illumination spot) and in the case where a defect exists on the semiconductor substrate, scattered light which is generated from such a defect is detected by a photodetector, thereby inspecting the defects on the whole surface of the semiconductor substrate.
In such a surface inspecting apparatus, generally, an intensity of a signal which is obtained from the photodetector is converted into a size of detected defect and used as an inspection result. Such a conversion is performed in such a manner that a calibrating wafer (wafer for calibration) adhered with a standard particle (generally, PSL: polystyrene latex sphere is used) whose particle size (diameter) has already been known is preliminarily measured before the inspection, a relation between an intensity of scattered light which is generated by the standard particle whose particle size has already been known and the intensity of the signal which is obtained from the photodetector in correspondence to it is previously calculated as a calibration curve, and the actual inspection wafer is inspected, the intensity of the signal which is obtained from the photodetector is applied to the calibration curve and converted into the particle size corresponding to the standard particle. Such a calibrating method has been disclosed in, for example, JP-A-2003-185588 or the like.